Patent Document 1 discloses a vehicle-mounted power storage device that selectively supplies and receives electric power with respect to an external power source device. When the external power source device is connected to a vehicle through a charging cable and the power source voltage of an auxiliary-device battery is equal to or smaller than a predetermined value, the vehicle-mounted power storage device prohibits electric power supply from the auxiliary-device battery to devices other than devices involved in updating of charging control programs.
According to a recent proposal, with a charging cable maintained in a state connected to a vehicle, charging may be held in a standby state until a later time zone in which the electric power is less expensive. However, the device disclosed in Patent Document 1 does not particularly set a restriction for when the power source voltage of the auxiliary-device battery is greater than the predetermined voltage. Therefore, by the time charging is performed with the charging cable maintained in the state connected to the vehicle, the electric power of the auxiliary-device battery is unnecessarily consumed by vehicle-mounted devices.